CN111823782B

CN111823782B - Pneumatic tire having apex with multiple rubber layers

Info

Publication number: CN111823782B
Application number: CN201911081856.5A
Authority: CN
Inventors: 曹永俊; 洪昌孝
Original assignee: Hankook Tire and Technology Co Ltd
Current assignee: Hankook Tire and Technology Co Ltd
Priority date: 2019-04-16
Filing date: 2019-11-07
Publication date: 2022-11-15
Anticipated expiration: 2039-11-07
Also published as: EP3725565B1; KR102204855B1; US20200331303A1; KR20200121939A; EP3725565A1; CN111823782A; US11485177B2; JP2020175880A; JP6985354B2

Abstract

The present invention relates to a pneumatic tire having apex with multiple rubber layers applied thereto, and more particularly, the present invention comprises: a sidewall portion formed by bending both sides of a tread portion, the tread portion being in direct contact with a road surface, the tread portion being a thick rubber layer; a bead core mounted to a rim of a vehicle; and a bead part provided in a manner of having different rubber hardness, and the present invention is characterized by comprising a carcass as an inner frame of a tire, turned up with a bead core of the bead part as a center, the bead part comprising: a first apex surrounded by the carcass and the turned-up carcass on the inner side of the tire; and a second bead filler disposed between the outer side surface of the turned carcass and the sidewall and rim liner, and using a plurality of rubber layers made of rubber layers having different properties to reduce weight and improve rolling resistance.

Description

Pneumatic tire having apex with multiple rubber layers

Technical Field

The present invention relates to a pneumatic tire having a bead apex, and more particularly, to a pneumatic tire having a bead apex using multiple rubber layers, which can control deformation of each portion by forming the bead apex from the multiple rubber layers.

Background

Generally, the structure of a tire is roughly divided into: a Tread portion (Tread) belonging to a rubber layer in contact with the road surface; a Carcass (Carcas) belonging to a belt ply inside a tire, supporting a load and bearing an impact, and having a high fatigue resistance to a bending and stretching movement during a running process to form a framework of the tire; a Bead (Bead) that functions to mount the tire on a Rim (Rim) of an automobile; and a Sidewall portion (Sidewall) as a side portion of the tire, protecting the carcass, and performing a tensile motion rich in flexibility.

Although such tires are being developed to have high performance and reduced weight, when the vehicle load is increased and the tires are reduced in weight, accidents due to insufficient bead durability occur.

Therefore, in the past, in order to reinforce the bead, a double bead structure has been manufactured, and such a structure can improve durability, but has a problem of increasing weight and rolling resistance.

In order to solve such problems, it is necessary to manufacture a tire capable of controlling deformation of each portion of the bead portion.

Documents of the prior art

Patent document

Patent document 1: korean granted patent publication No. 10-0578101 (2006, 05, 02)

Disclosure of Invention

Problems to be solved by the invention

The present invention provides a pneumatic tire having a bead apex using multiple rubber layers, wherein the second bead apex of the tire is formed of multiple rubber layers to control deformation of each portion of the bead apex, thereby reducing weight and improving rolling resistance, and compression deformation and shear deformation of a bead portion can be reduced by moving a line of a turned carcass inward.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other technical problems not mentioned can be clearly understood by those skilled in the art to which the present invention pertains from the following descriptions.

Means for solving the problems

In order to solve the above-mentioned technical problems, the present invention provides a pneumatic tire having an apex to which a plurality of rubber layers are applied, comprising: a sidewall portion formed by bending both sides of a tread portion, the tread portion being in direct contact with a road surface, the tread portion being a thick rubber layer; a bead core mounted to a rim of a vehicle; the invention is characterized in that the tire comprises a tire body which is used as an inner framework of the tire and is turned over by taking a bead core of the tire bead part as a center, and the tire bead part comprises: a first apex surrounded by the carcass and the turned-up carcass on the inner side of the tire; and a second bead filler disposed between the outer side surface of the turned carcass and the sidewall and rim liner, and using a plurality of rubber layers made of rubber layers having different properties to reduce weight and improve rolling resistance.

In an embodiment of the present invention, the second apex is formed in an elongated shape having a cross section gradually narrowing toward the upper end and the lower end, and is disposed in a shape in which the upper end is inclined outward of the tire with reference to a radius of the tire.

In an embodiment of the present invention, the second apex may be provided with: a first glue part located at the upper end of the second triangular glue; a third glue part located at the lower end of the second triangular glue; and a second rubber portion connecting the first rubber portion and the third rubber portion.

In an embodiment of the present invention, in order to reduce the weight and improve the rolling resistance, the first rubber portion, the second rubber portion, and the third rubber portion of the second apex are formed of rubber layers having different properties, so that the deformation of each portion of the second apex can be controlled.

In the embodiment of the invention, the modulus of the first rubber body part is set to be 3.70E +07, the loss factor is set to be 0.22, the modulus of the second rubber body part is set to be 6.00E +06, the loss factor is set to be 0.07, the modulus of the third rubber body part is set to be 7.00E +06, and the loss factor is set to be 0.12.

In an embodiment of the present invention, an upper end of the first rubber portion intersects with a second straight portion, the second straight portion forms an angle of 10 to 30 degrees with a first straight portion, and the first straight portion extends horizontally in a width direction of the tire from an intersection between a maximum width line of the tire and a maximum height line of the tire.

In an embodiment of the present invention, a lower end of the first rubber portion and an upper end of the second rubber portion intersect with a third linear portion, and the third linear portion and the second linear portion form an angle of 10 to 25 degrees with respect to an intersection point.

In an embodiment of the present invention, a lower end of the second plastic part and an upper end of the third plastic part intersect with a fourth linear part, and the fourth linear part and the third linear part form an angle of 10 to 30 degrees with respect to an intersection point.

In an embodiment of the present invention, a lower end of the third rubber portion intersects with a fifth straight portion, and the fifth straight portion and the fourth straight portion form an angle of 10 to 30 degrees around the intersection.

In an embodiment of the present invention, in the second apex, a first tangent portion parallel to a height direction of the tire is formed at a position where the fifth straight portion intersects with the turned-up carcass, and a lower end of the third portion is disposed so as to intersect with the first tangent portion.

In an embodiment of the present invention, the second apex includes a second tangent portion capable of inclining the first tangent portion by 0 to 5 degrees with respect to the tire outer direction, and the upper end of the third carcass portion and the lower end of the second carcass portion are disposed on the turned carcass intersecting the second tangent portion.

In an embodiment of the present invention, the second apex includes a third tangential portion capable of inclining the second tangential portion by 0 to 8 degrees with respect to the tire outer direction, and the upper end of the second carcass portion and the lower end of the first carcass portion are disposed on the turned carcass intersecting the third tangential portion.

In an embodiment of the present invention, the second apex rubber has a fourth tangential portion capable of forming the third tangential portion with an inclination of 0 to 10 degrees with respect to the tire outer side direction, and the upper end of the first rubber portion is disposed on the carcass turned over so as to intersect the fourth tangential portion.

Effects of the invention

According to the embodiment of the present invention, the pneumatic tire having the bead apex using the multiple rubber layers has the effect of reducing the compression deformation and the shear deformation of the bead portion by forming the second bead apex from the multiple rubber layers, and controlling the deformation of each portion of the bead apex, thereby reducing the weight and improving the rolling resistance, and by moving the turned carcass line inward.

The effects of the present invention are not limited to the above-described effects, and it should be understood that the effects of the present invention also include all effects that can be derived from the configuration of the invention described in the detailed description of the invention or the scope of the claims.

Drawings

FIG. 1 is a cross-sectional view of a pneumatic tire having an apex employing multiple rubber layers in accordance with one embodiment of the present invention.

Fig. 2 is a sectional view of a pneumatic tire having an apex using multiple rubber layers, in which a straight portion and a tangent portion are used, according to an embodiment of the present invention.

Fig. 3 shows the analysis results for explaining the rolling resistance of the conventional bead structure and the bead portion structure of the present invention to which the multiple rubber layers are applied.

Fig. 4 shows the results of Strain Energy Density (SED) analysis of the conventional bead structure and the bead portion structure of the present invention to which multiple rubber layers are applied, under air Pressure and Zero air Pressure (Zero Pressure) of a run flat tire (Runflat tire).

Description of reference numerals

100: pneumatic tire having bead apex with multiple rubber layers

110: sidewall portion

120: bead core

130: tyre body

131: turned-up carcass

140: first triangular glue

150: second apex

151: first colloid part

152: second colloid part

153: third colloidal moiety

160: rim gasket

170: intersection point

171: a first linear part

172: second straight line part

173: third straight line part

174: the fourth straight line part

175: fifth straight line part

181: first tangent part

182: second tangent line part

183: third tangent line part

184: the fourth tangent line part

Detailed Description

The present invention will be described below with reference to the accompanying drawings. The present invention can also be implemented in other different embodiments, and is therefore not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, portions that are not related to the description are omitted, and like reference numerals are given to like portions throughout the specification.

Throughout this specification, when a certain portion is described as being "connected (coupled, contacted, coupled)" to another portion, it means not only the case of "directly connecting" but also the case of "indirectly connecting" by interposing another member therebetween. In addition, when a certain portion is described as "including" a certain structural element, unless otherwise stated, it means that other structural elements may be provided, and it is not meant to exclude other structural elements.

The terminology used in the description presented herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise specified, singular expressions also include plural expressions. It should be understood that in the present specification, terms such as "comprises" or "comprising" are used to specify the presence of stated features, integers, steps, actions, structural elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, actions, structural elements, components, or groups thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a sectional view of a pneumatic tire having a bead apex using multiple rubber layers according to an embodiment of the present invention, and fig. 2 is a sectional view of a pneumatic tire having a bead apex using multiple rubber layers, in which a straight portion and a tangential portion are used according to an embodiment of the present invention.

Referring to fig. 1 to 2, a pneumatic tire 100 having an apex using multiple rubber layers of the present invention includes: the method comprises the following steps: a sidewall portion 110 formed by bending both sides of a tread portion, the tread portion being in direct contact with a road surface, the tread portion being a thick rubber layer; a bead core 120 mounted to a rim of a vehicle; and a bead part provided in a manner of having different rubber hardness, the bead part surrounding the bead core 120 and the bead apex, the carcass 130 surrounding the outside of the bead part, and a rim liner 160 provided on the outside of the carcass 130, and the present invention is characterized by including the carcass 130 as an inner frame of a tire, which is turned up with the bead core 120 of the bead part as a center, the bead part including: a first apex 140 surrounded by the carcass 130 and the turned carcass 131 inside the tire; and a second bead filler 150 disposed between the outer side surface of the turned carcass 131 and the sidewall 110 and the rim, and using a plurality of rubber layers made of rubber layers having different properties to reduce the weight and improve the rolling resistance.

The pneumatic tire 100 having the apex applied with multiple rubber layers of the present invention includes a carcass 130.

More specifically, the carcass 130 is turned around the bead core 120 of the bead portion as a framework inside the tire.

The bead portion includes a first apex 140 and a second apex 150.

More specifically, the first apex 140 is surrounded by the carcass 130 and the turned-up carcass 131 inside the tire.

That is, the carcass 130 is turned up to the outside of the tire around the bead core 120, and in this case, the first apex 140 is provided between the carcass 130 on the inside of the tire and the turned-up carcass 131.

Accordingly, the first bead filler 140 is surrounded by the carcass 130, and thus external impact can be absorbed and deformation of the bead portion due to a high load can be prevented.

The second bead filler 150 is disposed between the outer side surface of the turned carcass 131, the sidewall 110, and the rim cushion 160, and is formed of multiple rubber layers having different properties to reduce weight and improve rolling resistance.

More specifically, the second apex 150 is provided between the outer side surface of the turned carcass 131, and the sidewall 110 and the rim cushion 160 located on the outer side of the tire. That is, the inner side surface of the second bead apex 150 is bonded to the outer side surface of the turned carcass 131, the upper portion of the outer side surface of the second bead apex 150 is surrounded by the sidewall portion 110, and the lower portion is surrounded by the rim cushion 160.

Accordingly, the second bead filler 150 can absorb external impact between the outer surface of the carcass 130 and the sidewall 110 and the rim cushion 160, and prevent deformation of the bead portion due to a high load.

The second apex 150 has an elongated shape whose cross section gradually narrows toward the upper end and the lower end, and is disposed in a shape in which the upper end is inclined outward of the tire with respect to the tire radius.

In more detail, the sectional shape of the second apex 150 is formed in a shape elongated in the tire height direction so as to be gradually narrowed toward the upper end and the lower end of the elongated shape, the upper end of the sectional shape is directed toward the outside of the tire with reference to the radial direction of the tire, and the lower end is directed toward the bead core 120 side.

The second apex 150 has disposed in the longitudinal direction of the cross section: a first rubber part 151 located at the upper end of the second apex; a third rubber part 153 positioned at the lower end of the second bead filler; and a second rubber portion 152 connecting the first rubber portion 151 and the third rubber portion 153.

More specifically, the second apex 150 is made of three different materials, the first body part 151 is located at an upper end of the second apex 150, the third body part 153 is located at a lower end of the second apex 150, and the second body part 152 is located between the first body part 151 and the third body part 153 to connect the first body part 151 and the third body part 153.

Accordingly, the first, second, and

third rubber portions

151, 152, and 153 are made of materials having different properties, and thus the deformation of the tire can be controlled according to the external stress.

Furthermore, the Modulus (Modulus) of the first colloid portion 151 is set to 3.70e +07, the loss factor (Tan δ) is set to 0.22, the Modulus of the second colloid portion 152 is set to 6.00e +06, the loss factor is set to 0.07, the Modulus of the third colloid portion 153 is set to 7.00e +06, the loss factor is set to 0.12, and rubber layers different in Modulus and loss factor are applied according to the magnitude of deformation of the tire.

In more detail, the first, second, and

third rubber portions

151, 152, and 153 may be differently positioned to apply different external stresses, thereby making the tire differently durable and differently deformed. Accordingly, the deformation of the tire can be controlled by adjusting the modulus and the loss factor of the first, second, and

third rubber portions

151, 152, and 153.

That is, the rubber material has the advantages of high modulus, small loss factor, reduced side deformation, and good properties.

The upper end of the first rubber portion 151 intersects with a second straight portion 172, the second straight portion 172 forms an angle α of 10 to 30 degrees with a first straight portion 171, and the first straight portion 171 horizontally extends in the width direction of the tire from an intersection 170 between a maximum width line (S/W point) of the tire and a maximum height line (OD point) of the tire.

More specifically, a position where the tire maximum width line and the tire maximum height line intersect each other is designated as an intersection 170, a first straight line portion 171 is formed in a direction parallel to the lateral direction of the tire by the designated intersection 170, an upper end of the first rubber portion 151 intersects a second straight line portion 172, and the second straight line portion 172 forms an angle of 10 degrees to 30 degrees with the first straight line portion 171 with the intersection 170 as a center. That is, the upper end of the first rubber part 151 is located at a position where the second linear part 172 intersects the turned carcass 131.

A lower end of the first colloidal segment 151 and an upper end of the second colloidal segment 152 intersect with a third linear segment 173, and the third linear segment 173 forms an angle β of 10 to 25 degrees with the second linear segment 172 around the intersection point 170.

More specifically, the third linear portion 173 forms an angle of 10 to 25 degrees with the second linear portion 172, with the intersection point 170 as the center. The lower end of the first rubber portion 151 and the upper end of the second rubber portion 152 intersect the third linear portion 173.

That is, the lower end of the first colloidal segment 151 and the upper end of the second colloidal segment 152 are connected, and the third linear segment 173 is a boundary between the lower end of the first colloidal segment 151 and the upper end of the second colloidal segment 152.

The lower end of the second portion 152 and the upper end of the third portion 153 intersect with a fourth linear portion 174, and the fourth linear portion 174 and the third linear portion 173 form an angle γ of 10 to 30 degrees around the intersection 170.

More specifically, the fourth straight line portion 174 forms an angle of 10 to 30 degrees with the third straight line portion 173 around the intersection point 170. The lower end of the second plastic portion 152 and the upper end of the third plastic portion 153 are disposed to intersect the fourth linear portion 174.

That is, the lower end of the second plastic part 152 and the upper end of the third plastic part 153 are connected, and the fourth linear part 174 is a boundary between the lower end of the second plastic part 152 and the upper end of the third plastic part 153.

The lower end of the third rubber part 153 intersects with a fifth linear part 175, and the fifth linear part 175 and the fourth linear part 174 form an included angle δ of 10 to 30 degrees around the intersection point 170.

More specifically, the fifth straight portion 175 and the fourth straight portion 174 form an angle of 10 to 30 degrees with the intersection 170 as a center. The lower end of the third rubber portion 153 is disposed to intersect the fifth linear portion 175.

Accordingly, the first, second, and

third rubber portions

151, 152, and 153 are arranged to be divided by the first, second, third, fourth, and fifth

straight portions

171, 172, 173, 174, and 175, and thus, according to the magnitude of the strain of the tire, the strain of each portion is controlled, and the weight of the tire is reduced and the rolling resistance is improved.

The second apex 150 has a first cut line portion 181 parallel to the height direction of the tire formed at a position where the fifth straight portion 175 intersects the turned carcass 131, and the lower end of the third carcass portion 153 is disposed to intersect the first cut line portion 181.

More specifically, the first cut line portion 181 is formed parallel to the tire height direction at a position where the fifth straight line portion 175 intersects the turned carcass 131, and the lower end of the third carcass portion 153 is disposed with reference to the first cut line portion 181.

The second apex 150 has a second tangent portion that can form the first tangent portion at an inclination a of 0 to 5 degrees with respect to the tire outer direction, and the upper end of the third carcass portion 153 and the lower end of the second carcass portion 152 are disposed on the turned-up carcass 131 intersecting the second tangent portion 182.

More specifically, the second cut line portion 182 is formed such that the first cut line portion 181 has an inclination of 0 to 5 degrees with respect to the tire outer side direction, and the upper end of the third rubber portion 153 and the lower end of the second rubber portion 152 are disposed at the second cut line portion 182.

That is, the upper end of the third rubber portion 153 and the lower end of the second rubber portion 152 intersecting the turned carcass 131 can be set by the second tangent portion 182.

The second apex 150 includes a third cut portion 183, the third cut portion 183 is configured such that the second cut portion 182 is inclined at an angle b of 0 to 8 degrees with respect to the tire outer direction, and the upper end of the second carcass portion 152 and the lower end of the first carcass portion 151 are disposed on the turned-up carcass 131 intersecting the third cut portion 183.

More specifically, the third cut line portion 183 is formed such that the second cut line portion 182 is inclined at an angle of 0 to 8 degrees with respect to the tire outer side direction, and the upper end of the second rubber portion 152 and the lower end of the first rubber portion 151 are disposed at the third cut line portion 183.

That is, the upper end of the second rubber portion 152 and the lower end of the first rubber portion 151 intersecting the turned carcass 131 can be set by the third cut line portion 183.

The second apex 150 includes a fourth linear cut portion 184, the fourth linear cut portion 184 is capable of forming the third linear cut portion 183 with an inclination c of 0 to 10 degrees with respect to the tire outer direction, and the upper end of the first carcass portion 151 is disposed on the turned carcass 131 intersecting the fourth linear cut portion 184.

More specifically, the fourth linear cutting portion 184 is formed such that the third linear cutting portion 183 is inclined at an angle of 0 to 10 degrees with respect to the tire outer direction, and the upper end of the first colloid portion 151 is disposed at the fourth linear cutting portion 184.

That is, the upper end of the first rubber portion 151 intersecting the turned carcass 131 can be set by the fourth linear cutting portion 184.

Fig. 3 shows the analysis results for explaining the rolling resistance of the conventional bead structure and the bead portion structure of the invention to which the multiple rubber layers are applied.

Referring to fig. 3, it can be confirmed that in the Conventional tire (Conventional tire) and the run-flat tire, a plurality of rubber layers are applied to a portion where deformation is large, as compared with the Conventional bead portion structure using one rubber layer, and this bead structure can reduce deformation and improve rolling resistance.

Fig. 4 shows the results of strain energy density analysis of the conventional bead structure and the bead portion structure of the present invention to which multiple rubber layers are applied at the air pressure and the zero air pressure of the run-flat tire.

Referring to fig. 4, the bead structure of the present invention using multiple rubber layers can reduce the compression deformation of the SIR part, and the deformation of the bead part at each position can induce the optimal deformation of the tire characteristics, compared to all the conventional bead part structures in the pneumatic and zero-pneumatic states.

Thus, according to the bead part structure of the tire using the multiple rubber layers of the present invention, the second rubber part 152 can be formed of the multiple rubber layers according to durability and characteristics of the tire, thereby reducing weight and improving rolling resistance while having durability.

Further, the multiple rubber layers can be freely arranged at the positions of weak durability, and the deformation of each part of the second apex 150 can be controlled.

The above description is for illustrating the present invention, and it will be understood by those skilled in the art to which the present invention pertains that other embodiments can be easily modified without changing the technical idea or essential features of the present invention, and therefore, the above embodiments are intended to illustrate the present invention in all aspects and are not intended to limit the present invention. For example, each component described in a single mode may be implemented in a dispersed manner, and similarly, components described in a dispersed manner may be implemented in a combined manner.

The scope of the present invention is defined by the appended claims, and all changes and modifications that come within the meaning and range of equivalency of the claims are to be construed as being embraced therein.

Claims

1. A pneumatic tire having apex with multiple rubber layers applied thereto, comprising: a sidewall portion formed by bending both sides of a tread portion, the tread portion being in direct contact with a road surface, the tread portion being a rubber layer; a bead core mounted to a rim of a vehicle; and a bead portion provided so as to have different rubber hardnesses, the pneumatic tire having a bead apex to which multiple rubber layers are applied being characterized in that,

comprises a tire body as an inner framework of the tire, which is turned over by taking a bead core of a bead part as a center,

the bead portion includes:

a first apex surrounded by the carcass and the turned-up carcass on the inner side of the tire; and

a second bead apex disposed between the outer side surface of the turned carcass and the sidewall and rim, and using a plurality of rubber layers composed of rubber layers having different properties to reduce weight and improve rolling resistance performance;

the second apex is formed into an elongated shape having a cross section gradually narrowing toward the upper end and the lower end, and is arranged in a shape such that the upper end is inclined toward the outside of the tire with reference to the tire radius;

the second apex is provided with, in the longitudinal direction of the cross section thereof:

a first glue part positioned at the tail end of the upper side of the second triangular glue,

a third gum portion located at the lower end of the second apex, an

A second rubber portion connecting the first rubber portion and the third rubber portion;

in order to reduce the weight and improve the rolling resistance performance, the first rubber part, the second rubber part and the third rubber part of the second triangular rubber are composed of rubber layers with different moduli and loss factors so as to adjust the deformation of each part of the second triangular rubber,

the loss factor of the first plastic part is set to 0.22, the loss factor of the second plastic part is set to 0.07, and the loss factor of the third plastic part is set to 0.12.

2. The pneumatic tire with apex applying multiple rubber layers as set forth in claim 1, wherein the modulus of the first rubber body portion is set to 3.70E +07, the modulus of the second rubber body portion is set to 6.00E +06, and the modulus of the third rubber body portion is set to 7.00E +06.

3. A pneumatic tire having an apex using multiple rubber layers according to claim 1, wherein the upper end of said first rubber portion intersects a second straight portion, said second straight portion forming an angle of 10 to 30 degrees with a first straight portion extending horizontally in the width direction of the tire from the intersection between the maximum width line of the tire and the maximum height line of the tire.

4. A pneumatic tire having a bead apex with multiple rubber layers according to claim 3, wherein a lower end of said first rubber portion and an upper end of said second rubber portion intersect a third straight portion, and the third straight portion and the second straight portion form an angle of 10 to 25 degrees with respect to each other with the intersection point as a center.

5. The pneumatic tire having a apex using multiple rubber layers as set forth in claim 4, wherein a lower end of said second rubber portion and an upper end of said third rubber portion intersect a fourth straight portion, and an angle of 10 to 30 degrees is formed between said fourth straight portion and said third straight portion with respect to the intersection point.

6. A pneumatic tire having a bead apex with multiple rubber layers according to claim 5, wherein a lower end of said third rubber portion intersects a fifth straight portion, and said fifth straight portion forms an angle of 10 to 30 degrees with said fourth straight portion with the intersection as a center.

7. A pneumatic tire having an apex to which multiple rubber layers are applied according to claim 6, wherein in the second apex, a first tangent portion parallel to the height direction of the tire is formed at a position where the fifth straight portion intersects the turned carcass, and a lower end of the third rubber portion is disposed so as to intersect the first tangent portion.

8. A pneumatic tire having an apex using multiple rubber layers according to claim 7, wherein the second apex has a second tangent portion which makes the first tangent portion inclined at 0 to 5 degrees to the tire outer direction, and the upper end of the third carcass portion and the lower end of the second carcass portion are disposed on a turned carcass intersecting the second tangent portion.

9. The pneumatic tire having apex using multiple rubber layers according to claim 8, wherein the second apex has a third tangential portion which makes the second tangential portion have an inclination of 0 to 8 degrees with respect to the tire outer side direction, and the upper end of the second carcass portion and the lower end of the first carcass portion are disposed on the carcass turned over so as to intersect with the third tangential portion.

10. A pneumatic tire having an apex using multiple rubber layers according to claim 9, wherein said second apex has a fourth tangential portion capable of inclining said third tangential portion at an angle of 0 to 10 degrees with respect to the tire outer side direction, and the upper end of said first carcass portion is disposed on a turned carcass intersecting said fourth tangential portion.